To improve the dispersion of CuO nanoparticles in ammonium perchlorate (AP), CuO/AP nanocomposites are designed and the novel ceramic membrane anti-solvent crystallization (CMASC) method is applied to the nanocomposites synthesis. Typical experimental results demonstrate that nanocomposites with a size of less than 20m exhibit well-defined hexahedral-like structure and that the CuO nanoparticles are physically coated by AP crystals. The well-dispersion of CuO nanoparticles and preparation of superfine AP crystals can be achieved at one step. The nucleation and growth mechanism of nanocomposites is discussed. To explore the actual formation process of the nanocomposites, relevant experiments are designed and carried out. The results are well consistent with previous assumptions and verify that several parameters, including feeding rate, volume ratio of matched solvent and anti-solvent, can be employed to manipulate the size and morphology of the nanocomposites. The catalytic activity of CuO nanoparticles in the nanocomposites exhibits superior performance.